Due to the complexity of multiple spindle mechanisms of the kind employed in automatic screw machines and the like, difficult problems of lubrication are presented. Typically, the parts are simply flooded with oil; in addition to being relatively inefficient and wasteful, however, flooding techniques require oil recovery, and normally recirculation.
Moreover, components of such mechanisms are prone to excessive wear and premature exhaustion due to the tendency for metal debris and other foreign matter to enter between mating bearing surfaces. These problems are exacerbated in mechanisms that employ axially reciprocating spindles, since such action tends to drag foreign matter into and between the mating surfaces; in the case of automatic screw machines, for example, the zone of greatest exposure is the machining station that lies in front of the several spindles. Mechanical seals have of course long been used in an effort to ameliorate such contamination, but they are known to be quite ineffective.
Drissner U.S. Pat. No. 2,728,414, issued Dec. 27, 1955, provides a lubrication system for a machine having multiple spindles, in which oil is supplied through tubes to oil sleeves, sequentially indexed into proximity with one another.
Quinn et al U.S. Pat. No. 4,068,740, issued Jan. 17, 1978, provides a gear train in which one of the gears functions as a centrifugal oil pump.
In the apparatus disclosed in Osborne U.S. Pat. No. 4,344,507, issued Aug. 17, 1982, a threaded member is used to force lubricating fluid from a reservoir through internal bores and ports to an upper bearing assembly.
Sugioka et al U.S. Pat. No. 4,905,974, issued Mar. 6, 1990, provides a system in which rotatable oil tanks are used to lubricate the bearings of a turret-type machine.